PPAR-γ activation increases insulin secretion independent of CASK in INS-1 cells  

作　　者：Kai Zhang Qingzhao Yuan Jinyang Xie Li Yuan Yao Wang 

机构地区：[1]Department of Endocrinology, Zhongda Hospital, Institute of Diabetes, Medical School, Southeast University, Nanjing 210009, China [2]Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 210009, China

出　　处：《Acta Biochimica et Biophysica Sinica》2019年第7期715-722,共8页生物化学与生物物理学报（英文版）

基　　金：This work was supported by the grant from the National Natural Science Foundation of China (No.81570734 to Y.W.).

摘　　要：Peroxisome proliferator-activated receptor-γ(PPAR-γ) is expressed in pancreatic β cells and is involved in insulin secretion. However, the precise mechanisms remain unclear. Calcium/calmodulin-dependent serine protein kinase (CASK), which plays a vital role in the anchoring of insulin granules on pancreatic β cell membrane, is probably a downstream of the transcription factor PPAR-γ. The aim of the present study was to investigate the correlation among PPAR-γ, CASK and insulin secretion. We found that rosiglitazone (RSG) had a positive effect on the expression of CASK and PPAR-γ in INS-1 cells as shown by real-time polymerase chain reaction (PCR) and western blot analysis, but did not change the cellular location of CASK as shown by immunofluorescence assay. Knockdown of PPAR-γ significantly attenuated the mRNA and protein expression levels of CASK. ChIP-qPCR and luciferase assays showed that PPAR-γ bound with the Cask promoter, and promoter activity of Cask was elevated by RSG. RSG significantly enhanced the insulin secretion with potassium stimulation, but did not alter the insulin content as shown by potassium-stimulated insulin secretion assay. In addition, with RSG pretreatment, knockdown of Cask did not significantly affect the PPAR-γ activation-mediated insulin secretion. Moreover, electron microscopy demonstrated that with RSG pretreatment, silence of Cask did not change the number of vesicles anchored on the cell membranes compared with those in siCask-treated cells. Overall, the present study identifies that CASK is one of the PPAR-γ downstream targets and PPAR-γ exerts a positive effect on the expression of CASK in INS-1 cells. PPAR-γ activation increases insulin secretion independent of the upregulation of CASK.

关 键 词：INS-1 cells PPAR-Γ CASK ROSIGLITAZONE 

分 类 号：Q51[生物学—生物化学]